I got a message that my Event Log 80% full. What does this mean?

The Vista systems can record up to 100 system events in a history log. Because you have an Event Logging selection is made in field ∗90, a message was sent to the central station when the log was 80% full. If the log becomes full, new messages overwrite the oldest messages in the log. To disable this, just put a 0 in *90.